Mechanical jars are known to those skilled in the art. Mechanical jars are often used for retrieving downhole tools which have become stuck or lodged downhole in a borehole. A jar can be run downhole on the end of a tubing string, drill string, or wireline. The wireline is especially suitable for running a jar for it enables a great force to be stored in the resilient wireline which is exerted on a jar mandrel. This is because there are usually several thousand feet of wire rope connected between the jar socket and the above surface operation. Therefore great energy is stored into a wireline for use in jarring a member uphole.
Both mechanical and hydraulically actuated jars are known to those skilled in the art. Most jars of the mechanical and the hydraulic type are extremely complicated, and for this reason they often malfunction. This often presents a serious problem when working downhole in a borehole.
One should never put anything downhole in a borehole that he is not willing to lose. Some boreholes cost several million dollars. Any tool that is to be run downhole into a borehole is first carefully evaluated and scrutinized by the oil industry. Accordingly, it is desirable that any tool string have incorporated therein a jar so that should any part of the string become stuck downhole, there is a likelihood that the jar can provide sufficient up-thrust to unstick the stuck tool or fish. It is not humorous that the jar which is suppose to obviate a fish often becomes a fish itself, and thereby compounds the problem of the first fish for now there are two fishes to be retrieved from the borehole.
The present invention comprehends a mechanical jar for use downhole in a borehole which stores and releases energy in a unique, novel, and unobvious manner.